Method of making alloy steels



Patented Oct. 23, 1928.

UNITED STATES y isa-gee pxreirir 1 CHARLES MCKNIGHT, JR., OF SEWICKLEY, PENNSYLVANIA, ASSIGNOR T THEINTER- NATIONAL NICKEL COMPANY, OF NEW YORK, N. Y., A CORIEORATION' OF NEW JERSEY.

METHOD OF MAKING ALLOY STEELfi.

No Drawing. Application filed June 8, 1925, S.erial'No. 35,788. Renewed March 18, 1928.

My invention relates to the making-of alloy steel from ferrous materials which contain,

a considerable or large percentage of silicon.

The invention relates especially to the 6 manufacture of alloy steels in the electric furnace, although Within my broader claims.

it may be used for any other methods of steel manufacture.

In the making of such alloy steels,,especially 1c in the electric furnace, manufacturers have had much difliculty in casting due to sudden and violent evolution of gases when the metal in the mold is near the solidification point.

Many ingots have been scrapped on account of this wildness in the mold. This action has occurred intermittently and .without on this subject, I have discovered that the' main cause for this inexplicable action has been the presence of silicon-bearing material in the charge from which the alloy steel is made. I have also discovered that this injurious action can be substantially done away with by reducing the silicon below 10%, and preferably below .05% during the working of so the charge.

In the ordinary.use of an electric furnace for making allo steels, the charge is melted down under oxidizing influences with a black or melt down slag, after which this slag a5 is removed and white or finishing slag fed to the bath and reducing conditions provided during the remainder of the heat. I have found that if, during the oxidizing period, the

' siliconis burnt out of the charge to reduce as it to a point less than 10%, and preferably less than 05%, the difficulty above referred to is removed. Thereafter silicon may be added, if a normal or high silicon content is desired, without producing wildness or sudden .4 rising of the metal in the mold.

' I have also found that the same beneficial effect is obtained where chromium or nickel or both are added to the charge before casting. In the making of many if not all of m these alloy steels, this same difiiculty of wildness in the mold has occurred. and I have found it to be largely due to the fact that charge prior to the addition of the alloying metal or metalloid.

In carrying out my invention, the silicon may be removed by oxidizing it to silica in any desirable manner, preferably by boiling or exposing it to an oxidizing atmosphere, and also by adding oxides to the bath or using oxides in the charge. In any event the silicon should be reduced to below 10% and preferably below 05%, after which the heat may be conducted in the usual manner to bring the bath to the desired analyses and to the quiescent state desirable to insure sound metal in the mold.

IVhile the invention is especially desirable in the making of alloy steels in electric furnaces, it is also applicable to and highly desirable in the manufacture of alloy steels in other ways, as for example in the open hearth. In all cases, the silicon should be reduced to the low point above referred to prior to the addition of the alloying ingredients, which may be and preferably'are added in the furnace prior to tapping.

The invention is especially desirable where the charge contains material having a considerable or large percentage of silicon, such for example, as high silicon scrap, whether the scrap contains nickel or chromium or other alloying metal. y

In the present manufacture of alloy steel, much of the scrap metal does contain considerable proportions of silicon, and I have discovered that if this silicon is not reduced below a critical percentage, the trouble with sudden rising or wildness of the steel in the mold occurs.

Many variations may be v..made in the method of making the steel, and other changes may be made Without departing from my invention.

I claim:

1. The method of stabilizing thesolidification of an alloy steel casting formed from scrap initially having ahigh silicon content, which consists in'melting the metal under oxidizing conditions until the silicon content is below a critical point, wherein't-he silicon does not exceed 1%, subjecting the-metal to a reducing condition and adding alloying materials thereto.

2. The method of stabilizing the solidification'of an alloy steel casting formed from ice scra initially having a high silicon content, whic consists in melting the metal under oxidizing conditions until the silicon content has been reduced to a point where it indicates a satisfactory as condition in the metal,

thereafter treatlng the metal under a reducwhere a satisfactory gas condition in the metal is indicated, thereafter treating the metal in-a reducing atmosphere and adding alloying material.

4. The method of producin in a high silicon content, which consists in me ting the charge in an electric furnace and exposing the same to an oxidizing atmosphere, reducing the silicon content to below .05%, thereafter subjecting the metal to a reducingcondition and adding alloying materials, and casting the metal,

5. In the manufacture of substantially sound castings of alloy steel from ferrous charges having a silicon content considerably above .10% and also relatively high inmetal alloy content, the steps consisting of oxidizin the said charge in molten condition until silicon reduction to a point not exceeding a casting hav- 10% indicating that troublesome gases are sufliciently eliminated, then working the heat until the proper conditions are attained, then deoxidizing and then casting the refined 'ma-" terial. 1 a e 6. In the manufacture of substantially soundcastings of alloy steel from ferrous charges having a silicon con-tent considerably above 10% and also relatively high in metal alloy content, the steps consisting of oxidizin the said charge in molten condition until silicon reduction to a point not exceeding.

' above .10% and also relatively high in metal alloy content, thesteps consisting ofoxidizing the said charge in molten condition until silicon reduction to a point not exceeding 10% indicating that troublesome gases are sufficiently eliminated, then working the heat until the proper conditions are attained, then adding alloy material and deoxidizing, and then casting the refined material.

In testimony whereof I havev hereunto set my hand.

- CHARLES MOKNIGHT, JR. 

